Concerned shower pump not installed properly by plumber

[CornflakeGrrrl79]

To cut a long story short, we have had a shower pump fitted by property maintenence company as part of new en-suite to boost a feeble shower (gravity fed). The chap it seems didn't know a lot and we have a had a second opinion that the wrong pump has been used and not installed correctly to boost the system. I am asking if anyone can back up this is the case before we take this further.
Gravity fed shower - cold tank in loft, hot cylinder in airing cupboard, same floor as en-suite. He has set up the pump to boost hot water and has left the cold water running directly to the shower from the header tank. This means a scolding powerful shower that is pathetic if you turn it to a cooler more bearable temperature. Doing some reading I cannot see this set up being advised anywhere - either hot & cold both go through a twin pump or the cold is mains pressure fed. Hopefully I have included all the relevant info if anyone can (helpfully) suggest this chap really didn't have a clue. Thanks.

 

[SimonH2]

The chap didn't have a clue. In your situation, it needs a dual pump so it boosts the pressure of both the hot and cold supplies. Ideally the hot supply should be taken from it's own tapping on the cylinder, and the cold should come from it's own connection to the header tank. In practice, if you use shared feeds then you get a bit of variation in flows and temperatures when other taps are used - how much this matters will depend a lot on how good the thermostatic shower valve is.

I have seen it done where a pump is used on the hot, but the cold is taken form the mains - but this does need a fairly decent thermostatic shower to cope with the pressure imbalance and variations.

 

[Pumpman6]

Agree 100% with SimonH2.